Published online by Cambridge University Press: 10 February 2011
This paper will describe the generation of micro- and sub-microcrystalline structures in two Ni-based alloys that are typically strengthened by phases, such as γ′ and γ″+δ. The relationship between the superplastic behavior and microstructure will be discussed. High strain deformation processing in the temperature range of 0.9 Tm to 0. 6Tm results in reduction of the initial coarse-grained structure (>100 µm) to a range of structures including microcrystalline (MC) (grain size <10 µm) and sub-microcrystalline (SMC) (grain size <1 µm) with increasing deformation. The influence of alloy chemistry and constituent phases on dynamic and static recrystallization is considered, and their effect on grain refinement is described. Low-temperature and high strain rate superplasticity can be observed in dispersionstrengthened alloys with SMC structures. It was established that in dispersion-hardened Ni alloys with SMC structures, superplasticity can be observed at temperatures 200-250°C lower than in alloys with MC structure.